THE SECRETORY MATERIAL OF THE SUBCOMMISSURAL ORGAN OF THE CHICK-EMBRYO - CHARACTERIZATION OF A SPECIFIC POLYPEPTIDE BY 2-DIMENSIONAL ELECTROPHORESIS

The subcommissural organ (SCO) is a cerebral gland that releases into the cerebrospinal fluid a carbohydrate-rich glycoprotein which condens es to form Reissner's fiber (RF). Western blots from two-dimensional g el electrophoresis were stained with lectins (Concanavalin-A, wheat ge rm agglutinin) and anti-bovine WF serum to identify the secretory prod ucts of the chick embryo SCO. Immunohistochemical investigations showe d that the anti-bovine RF serum reacted exclusively with the secretion of the SCO. Comparative protein patterns of SCO, pineal organ and cer ebral hemisphere extracts allowed us to characterize a specific polype ptide in the SCO electrophoretic profiles. The polypeptide was a highl y acid compound (isoelectric point of 4.7) with a high molecular weigh t (390 kDa). On Western blots only this component was immunoreactive w ith the RF antiserum and it exhibited an affinity for the two lectins. On the basis of these results, this polypeptide may be considered as a specific component of the secretory material synthesized by the SCO cells of the chick embryo.